Hello,

I have problems with a 22kW MM440 VFD (6SE6440-2UD32-2DA1) running in closed loop vector, it keeps triggering F0023 (output fault) at random times, I have checked the connections, cables between the VFD and motor (there's also no extra connections between them) and the motor (insulation test and winding resistance test @4A, all seems correct. The motor settings are also set according to the motors identification plate.

Measuring phase currents at the output there's not much difference when the motor runs at 20Hz+ (motor often runs at low frequency, down to 0.15Hz so measuring at those speeds is a problem)

Can anyone help with this issue?

Thanks,
Tomasz

I suggest the fault may be with the motor, even though you have tested it, an insulation resistance is not a sure method. The reason being that the insulation test will be testing windings to ground, this test cannot test breakdown between windings, which happens prior to the windings failing to ground.

Is it possible to replace the motor as a temporary measure?

There is test equipment available which can test between windings, and to ground at high Voltage.

Also:

The motor is being operated for a short time at 0.15Hz, this will create a sever stress to the IGBT, transistor output stage. This is due to the extended period for the junction to pass current.

Please come back if i can help further, or if you have resolved this problem.

Tractor

Our current suspicion is on the motor, although as I said, it has been tested both for insulation resistance (1kV test) and winding resistance, which showed the windings all having very close resistance.

We recently replaced the VFD because the old one had broken plastics which caused a lot of communication errors due to bad contacts, since replacing it we had this specific error quite often.

The application also has 2 identical sets of VFD + motor which work alternatively (it's 2 paper unwinders on a printing machine) switching motors between them is a lot of work, so we'll likely get a new motor to be sure and not have to do the work twice

I can understand replacing a motor in a machine, just for the purpose of fault diagnosis can be a difficult decision to make.

To have confidence in the motor I would suggest you have it tested with a 'Hi Pot Tester'. This is an expensive test device which you would not want to purchase, but these units are usually used by motor rewinders. These companies can visit site and test the motor in situ, to be certain that you are changing the correct motor; important for machines with motors buried deep.

Motors initially breakdown between windings of the same coil, at points where the windings overlap, this will be a discharge or spark through an insulation 'pin hole'. A motor in this condition operating from a sinusoidal supply for many months without and trouble, but an inverter drive will react to this. 

Motor windings operating from an inverter are subject to very high Voltages, in excess of 1000V, and it is this pressure which can cause breakdown of interwinding insulation. It is this breakdown which is difficult to detect, an insulation tester cannot detect this and a resistance measurement can be an indication, but not reliable because the test Voltage is low.

The 'Hi Pot Tester', is connected to the three terminals, coils are energised with high selectable Voltages, the charge time is measured, and from this a defective coil can be reliably identified, and you can be sure the correct motor is being replaced.

I have been in this position with deep borehole pumps, an incorrect diagnosis can be difficult to explain later.

I hope this goes well, come back if I can help further.

Tractor

Tombo, thank-you for the reply, it is good to be able to follow a fault through.

Many thanks

Tractor